Rigid pipe laying apparatus

ABSTRACT

A trencher adapted to be secured to graders and like construction equipment is provided with a rearwardly and downwardly sloping pipe passageway which terminates at the aft end of the trencher and exhibits a gentle curvature permitting elastic deflection of the pipe as it moves through the passageway. The trencher is rigidly supported from the grader frame at the forward end above a throw-out plate and at a rearwardly spaced intermittent point to assure the formation of a straight line trench having a closely controlled and constant depth. Relatively rigid, endless pipe, which may include intermittent T-sections, is laid out over the ground, picked up by a pipe guidance and suspension device mounted to the forward end of the grader, moved into and through the passageway and placed into the trench as the grader moves along.

United States Patent Wyatt 1 May 23, 1972 [54] RIGID PIPE LAYINGAPPARATUS Primary Examiner-Jacob Shapiro [72] Inventor. Wyatt, PO. Box8, Esparto, Alto Townsend and Townsend [22] Filed: June 1, 1970 ABSTRACT[21 App} 42,401 A trencher adapted to be secured to graders and likeconstruction equipment is provided with a rearwardly and downwardlysloping pipe passageway which terminates at the aft end of the [52] U.S.Cl ..61/72.5, 37/80 trencher and exhibits a gentle curvature permittingelastic [51] Int. Cl. ..E02f 5/10, F161 l/OO deflection of the pipe asit moves through the passageway. The [58] Field of Search ..6l/72.5,72.6, 72.7, 72.1, trencher is rigidly supported from the grader frame atthe for- 61/72.2; 37/193, 80 ward end above a throw-out plate and at arearwardly spaced intermittent point to assure the formation of astraight line 5 References Cited trench having a closely controlled andconstant depth. Relatively rigid, endless pipe, which may includeintermittent T- UNITED STATES PATENTS sections, is laid out over theground, picked up by a pipe guidance and suspension device mounted tothe forward end 536,339 3/1895 Hanneborg ..6l/72.5 of the grader movedinto and through the passageway and 1,991,919 2/1935 Bruins ..61/72.5placed into the trench as the grader moves along. 3,528,255 9/1970Blinne.... ..6l/72.6 3,170,301 2/1965 Kelley ..6l/72.l X 12 Claims, 5Drawing Figures RIGID PIPE LAYING APPARATUS BACKGROUND OF THE INVENTIONUnderground pipe laying, particularly the laying of relatively smalldiameter pipe as is frequently encountered on irrigation projects,requires the laying of often thousands of feet of pipe. Trenches for thepipes must be opened, the pipe laid and, thereafter, the trenches mustbe closed again. This involves substantial and costly labor.

To reduce labor costs attempts have been made to mechanize the pipelaying by first providing automatic trenching machines and then layingthe pipe and closing the trenches. Trenching machines, however, arerelatively expensive and, under adverse soil conditions such as gravel,exhibit costly wear and tear. Moreover, the pipe must still be placed inthe trench and covered with soil.

It is also known to provide a self-propelled vehicle, such as a tractor,store thereon a long, coiled length of flexible pipe, and lay the pipein a trench opened by a conventional trencher mounted to the tractor.These devices usually provide a plowshaped trencher that extendsforwardly or rearwardly of the tractor and is suspended therefrom in acantilever manner. The substantial pressures to which the trencher issubjected, particularly when working in hard soil, requires that it isrelatively short. The flexible pipe is moved through a passagewaydefined by the trencher into the open trench. The relatively shortnessof the trencher requires a sharp curvature of the pipe laying passagewayso that semi-rigid or rigid pipe cannot be accommodated in thepassageway.

Moreover, the installation of prior art pipe laying devices requiresextensive alterations and/or additions to available general purposeequipment such as tractors or cats. These alterations and additionsinclude, aside from the trencher per se, additional supporting frames,mounting linkages and the necessary hydraulics to operate the trencherand enable its raising and lowering. The alterations and additions arecostly and, when not in use, are bulky and can inhibit maneuverabilityand/or the drivers visibility. Prior art approaches to the simultaneoustrench digging and pipe laying, particularly the laying of semi-rigidand rigid pipe, have therefore not been very satisfactory.

The present invention provides apparatus for forming a trench andplacing a continuous string of relatively rigid pipe into the trench.Briefly, the apparatus comprises an elongate, narrow body having aforward end and an aft end, ground moving means secured to the forwardend for forming a trench in the ground through which the body can bedrawn and pipe guidance means extending over the length of the body. Theguidance means slope rearwardly and downwardly from an upper forward endof the body and terminate in a substantially horizontal position at alower aft end of the body. The guidance means has a curvature of asufficient curvature radius to enable the elastic deflection of pipemoving through the passageway. First mounting means for connection ofthe forward end of the body to a drawing vehicle, and second mountingmeans spaced rearwardly of the first mounting means for connection of anintermediate body portion to the drawing vehicle are provided to firmlyguide and position the apparatus and control the orientation and depthof the trench formed by the ground moving means while enablingcontinuous lengths of relatively rigid pipe to pass through the pipeguidance means into the trench.

In the preferred embodiment of the invention the body is defined bylaterally spaced upright plates which define side walls of the gentlycurved, downwardly and rearwardly oriented pipe passageway. Theapparatus can be mounted to conventional graders having forward and aftdrive and tracking wheels and a relatively high frame without the needfor altering the vertically movable accessory attachment yoke or addingadditional equipment, such as hydraulics, to the grader. The substantialspacing between the forward and aft wheels of the grader enables the useof relatively long bodies which have a length greatly in excess of thatpossible with prior art pipe laying devices. The great length is firmlysupported by longitudinally spaced forward and aft connection meansattached to the vertically movable grader yoke to stabilize theapparatus, maintain it in a straight path when it is drawn through theground and control the trench depth and maintain it constant.Additionally, the connection means permit limited lateral movements ofthe aft end of the body so that curved trenches of a relatively largecurvature radius can be formed.

The apparatus of the present invention is simple to construct,relatively lightweight and is of a sufficient size, particularly inlength, so that even rigid steel pipe consisting of a mu]- tiplicity ofjoined steel pipe sections can be laid by simply passing the pipe over asuspension roller mounted forward of the grader, through the passagewayof the trencher and into the dug trench. Pipe laying speeds of as muchas ten times the pipe laying speeds attainable with prior art equipmentare possible with the apparatus of the present invention. Substantialcost savings are thus assured. In addition, significant cost savings areprovided by the present invention through the simplicity of thetrencher, its ease of installation without substantial and costlyalterations to equipment, and through the elimination of specialequipment such as separate trench diggers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view ofthe rigid pipe laying apparatus of the present invention mounted to agrader;

FIG. 2 is an enlarged plan view of the pipe laying apparatus;

FIG. 3 is an enlarged side elevational view of the pipe layingapparatus;

FIG. 4 is a front elevational view, taken on line 44 of FIG. 3; and

FIG. Sis a sectional view taken on line 5-5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, arigid pipe laying apparatus 6 constructed in accordance with the presentinvention depends from a vertically movable yoke or subframe 8 disposedbelow a main frame 10 of a drawing vehicle such as a conventional grader12. The yoke comprises independently movable forward and aft members 97and 98 secured to hydraulic actuators 14 and 16, respectively, forraising and lowering it and pipe laying apparatus 6. Grader 12 is of aconventional construction and includes tracking means such as spacedapart forward wheels 17 and aft drive wheels 18. The rigid pipe layingapparatus is disposed in the space between the forward and aft wheelsand below main frame 10. During operation yoke 8 is lowered until thebottom of the pipe laying apparatus is disposed below ground 22. Whenthe grader moves in a forward direction the pipe laying apparatus formsa trench 24 centered between the left hand and right hand wheel sets. Anendless length of pipe 26 comprising end-to-end connected pipe sections28 is passed from a forward end 30 of the pipe laying apparatus to anaft end 32 where it is deposited on trench bottom 34.

Referring now to FIGS. 2 through 5, pipe laying apparatus 6 comprises amain trench forming body 36 defined by laterally spaced upright plates38 and 40 which extend from forward end 30 to aft end 32 of the body. Agenerally U-shaped brace 42 is disposed over the upright plates at theirforward ends and welded thereto. The brace includes a downwardly andforwardly sloping edge 44 onto which a high-strength, abrasionresistantthrow-out plate or tooth 46 is demountably secured to permit its readyreplacement. The tooth slopes forwardly and downwardly and terminates ina cutting edge 48 horizontally aligned with a lower edge 50 of body 36.

A gently curved pipe passageway 52 is disposed between plates 38 and 40and slopes in a downward direction from the upper forward end to thelower aft end of the body 36 where the passageway has a substantiallyhorizontal orientation. In the preferred embodiment of the inventionplates 38 and 40 define the sides of the passageway, which has arectangular configuration and a height exceeding its width, and parallelupper and lower transverse webs 54 and 56 connected, e.g. welded to theplates define the top and bottom of the passageway. The overall width ofbody 36, as determined by the required width of the passageway, isthereby held to a minimum. The webs have a substantially continuouslarge radius curvature to enable the passage of semi-rigid pipe, such asPVC pipe, or rigid pipe, such as standard steel pipe by merelyelastically deflecting such pipe so that it returns to its originalstraight configuration when it leaves the passageway.

For the laying of two inch PVC or I 4 inch steel pipe a pipe layingapparatus having an overall body length of about feet, a heightdifferential of pipe passageway 52 between the forward and aft ends ofabout inches and a substantially continuous curvature of the passagewaybetween its forward and aft ends provides a sufiiciently large curvatureradius so that the pipe deflects elastically as it passes through thepassageway. For larger diameter pipe, say 4 inch PVC or 2 inch steelpipe, an overall body length of about 17 feet with a height differentialbetween the forward and aft ends of the pipe passageway of about inchesagain provides a sufficiently large curvature radius for the passagewayso that the 2 inch steel pipe passing therethrough deflects elastically.For other pipe diameters the dimensions of the passageway, and therewithof body 36, are suitably adjusted.

A tubular pipe guidance member 58 is preferably secured to body 36 andextends forwardly thereof. The tubular member terminates in an outwardlyflaring mouth 60 and is aligned with passageway 52. The tubular memberextends the pipe passageway forward towards, and if desired, past theaxles of forward wheels 17. Although it is preferred to constructpassageway 52 in the above described manner by providing upper and lowerwebs 54 and 56 tubular member 58 can be extended rearwardly over thelength of body 36 to body aft end 32 to fully define passageway 52. Thisembodiment of the invention has the advantage that the tubular memberand the passageway can be prefabricated, In that instance the tubularmember is suitably secured, e.g. welded to upright plates 38 and 40.

To maintain body 36 of the pipe laying apparatus steady when it is drawnthrough the ground and prevent it from moving in lateral or verticaldirections, which would result in a trench 24 of uneven depth and cancause wedging of the body and substantial friction exerting excessivepower demands on the grader a two point suspension for the body isprovided. A first, forward connector 62 comprises a bracket 64 that issecured to brace 42 with a horizontally disposed pivot pin 66. Atransverse web 68 of the bracket includes releasable connection meansfor removably securing the bracket and forward end 30 of body 36 to thegrader. The grader has forward cross bar 70 with a plurality ofrectangular apertures (not separately shown) engaging two and preferablythree or more upright posts 72 extending from web 68 and defining theconnection means. The posts are shaped so that they fit snugly into theapertures in cross bar 70 and they are triangularly arranged (see FIG.2) with the center post being the forwardmost post to match thearrangement of the apertures in cross bar 70. The posts further includeslots 74 for securely connecting them to the cross bar in a knownmanner. Connection means for use with drawing vehicles having differentattachment devices and configurations can be substituted as necessary.

A second rear connector 76 is defined by an upright post 78 which issecured to a portion of body 36 intermediate its ends, preferably closerto aft end 32 than to forward end 30. A lower universal joint 80 betweenposts 78 and body 36 is defined by transverse pins 82 and 84, a pair ofspaced, opposing plates 38 and a block 90 disposed between and securedto plates 88. An upper universal joint 92 is similarly constructed asthe lower joint and its free end is secured to a substantiallyhorizontal connection plate 94 including mounting holes 96 for securingthe plate to a rearwardly positioned member 98 of yoke 8. Theuniversally movable second connector maintains body 36 steady as it isdrawn through the ground, but permits some slight lateral movementsbetween yoke 8 and aft end 32 of body 36 due to play in forwardconnection 62 and deflection of the body so that grader 12 can movealong gentle, large radii curves without undue edging of the body forcutting gently curved, large radii trenches.

In operation pipe laying apparatus 6 is attached to a drawing vehiclesuch as grader 12 which has sufficient top clearance and frame length toenable the two point overhead suspension of body 36. The pipe layingapparatus can be installed on the grader without changes or alterationsin its structure or hydraulic system by merely securing connection means62 and 76 to independent forward and aft members 97 and 98 of yoke 8.This permits the leveling of pipe laying apparatus 6 by suitably raisingor lowering the forward and/or aft yoke members.

Pipe sections 28 are laid end-to-end adjacent the desired path andconnected with pipe connectors 100 or T-fittings 102 which permit themounting of risers (not shown) after the pipe has been placed in trench24.

A pipe pick-up device 104 is mounted to the forward end of grader 12. Itcomprises a roller 106 mounted between bars 108 that depend downwardlyof the vehicle frame or a horizontally disposed forwardly extending beam110 secured to the vehicle frame.

Pipe laying commences by hoisting the end of the pipe string over thepick-up device and placing it into passageway 52. The forward movementof grader 12 results in the cutting of trench 24 to the set depth bylifting ground overlying throwout plate 46 upwardly and forming uprighttrench side walls which reduce the friction on upright plates 38, 40 ofbody 36. The vertically rigid connection between yoke cross bar 70 andforward end 30 of body 36 provides for excellent depth control andmaintains the trench depth constant even under adverse, e. g. hard soilconditions.

The endless pipe string passes over pick-up device 104, into mouth 60 oftubular member 58 and through passageway 52 into the trench. As thegrader moves along its path pipe is continuously lifted off ground 22 bypick-up device and passes continuously through the passageway 52.Relatively high speeds of as much as 300 feet per minute for the trenchand pipe laying operation can be attained.

In irrigation applications pipe risers (not separately shown) areinstalled in TS 102 spaced along the length of the pipe string. Suchinstallation requires that the Ts face upwardly. By constructingpassageway 52 so that it has a rectangular cross-section, a widthpermitting passage of the T-fittings and a height permitting passage ofthe open, transversely extending connection of the fitting whilepreventing it to rotate sideways, the desired orientation of thefittings after the pipe is deposited on the trench bottom isautomatically obtained. Moreover, by constructing passageway 52 in thismanner so that the minimum transverse dimension of the pipe string is ina lateral plane while the maximum transverse dimension (e.g. at theT-fittings) is in a vertical plane, the width of body 36, and therewiththe width of the dug trench can be minimized to reduce power consumptionand/or enable a speed-up in the work.

After pipe has been laid the trench is closed. Where no further workneeds to be done on the pipe string, e.g. where risers or the like neednot be installed, the trench can be closed by providing grader 12 with asuitable blade mounted behind of body aft end 32 which returns throw-upground into the trench and, preferably, which compacts the ground.

I claim:

1. Apparatus for laying relatively rigid, continuous lengths of pipebelow ground with a towing vehicle having a vehicle frame spaced aboveground between forward and aft traction means, the apparatus comprising:an elongate, rigid, narrow body having a forward end and an aft end,ground moving means forming an integral part of the body for forming atrench in the ground through which the body can be drawn, a

tubular passage for the pipe including a tubular member projectingforward of the forward end and terminating in a pipe receiving mouthportion for guiding the pipe into the tubular passage, the passageextending over the length of the body, sloping rearwardly and downwardlyfrom an upper forward end of the body and terminating in a substantiallyhorizontal position at the lower aft end of the body, the passage havinga curvature of a sufficient curvature radius so that pipe in the passageis only elastically deflected, first mounting means for connection ofthe forward end of the body to the frame aft of the forward tractionmeans, and second mounting means spaced rearwardly of the first mountingmeans for connection of an intermediate body portion to the frame aft ofthe first mounting means and forward of the aft traction means tothereby firmly guide and position the apparatus and control theorientation and depth of the trench formed by the ground moving meanswhile enabling continuous lengths of relatively rigid pipe to passthrough the passage into the trench.

2. Apparatus according to claim 1 wherein the second mounting meansincludes means permitting lateral movements of an aft portion of thebody with respect to a vertical axis through the first mounting means toenable the formation of curved trenches.

3. Apparatus according to claim 1 wherein the ground moving meanscomprises a substantially flat throw-out plate mounted to the forwardend in a forwardly and downwardly sloping position for lifting andthrow-out of ground to form the trench whereby lateral pressure againstthe body and friction are reduced.

4. Apparatus according to claim 1 wherein the passage has a rectangularcross-section and a height exceeding its width.

5, Apparatus according to claim 1 wherein the first mounting meanscomprises a mounting bracket pivotable about a substantially horizontalaxis and secured to the body portion adjacent the forward end, andincluding at least three upright connection members arranged in a wedgeformation through mating apertures in a yoke of the drawing vehicle.

6. Apparatus for connection to a draw vehicle having a main frame,forward and aft tracking means and a raiseable yoke disposed below theframe and intermediate the tracking means, the yoke including means forattaching working accessories thereto, the apparatus comprising: trenchforming means for expelling a volume of ground to form an elongatetrench when the vehicle moves over the ground, means positioning thetrench forming means aft of the forward tracking means and securing thetrench forming means to the yoke, means defining an elongate passagewaysloping rearwardly and downwardly, the passageway extending oversubstantially the full length of the trench forming means, thepassageway terminating in a substantially horizontal aft end sectionrearwardly of the trench forming means and having a radius of curvaturesufficiently large to effect elastic deformation of semi-rigid and rigidpipe passing through the passageway, means connecting the passagedefining means with the trench forming means, and means spacedrearwardly of the first connection means, attached to the yoke andconnected to an aft portion of the trench forming means forsubstantially rigidly holding an aft portion of the trench forming meansagainst vertical movement to guide and stabilize the trench formingmeans when it is drawn through the ground.

7. Apparatus according to claim 6 wherein the passage defining meansincludes means defining a substantially rectancluding a substantiallyflat, forwardly and downwardly sloping plate for the throw-out of soilrom the trench and means maintaining a predetermined trench shape over adistance rearward of the throw-out plate;

a gently curved, downwardly and rearwardly sloping pipe passageextending over substantially the full length of the trencher from anupper forward end to a substantially horizontal aft lower endsubstantially flush with a trench bottom, the passageway being enclosedby the trench form maintaining means, the radius of curvature of thepipe passage being sufficiently large so that pipe in the passage isonly elastically deformed and returns to its original shape upondischarge from the passage;

means connecting a forward trencher end to the frame at a location onthe frame forward of the aft wheels for stabilization of the trencherwhen it is drawn through the ground and maintaining the depth of thetrench bottom substantially constant.

9. Apparatus according to claim 8 wherein the passage defining means ispositioned so that relatively rigid pipe extending forward of theforward trencher end extends above a forward wheel axis, and furtherincluding pick-up means movably supporting a section of substantiallyrigid pipe for ward of the wheel axis at an elevation enabling elasticdeflection of a continuous length of pipe from the passage definingmeans over the pick-up means and onto the ground supporting the pipestring.

10. Apparatus according to claim 9 including a vertically movable yokecarried by the frame and wherein the first and second connection meansconnect the trencher to the yoke to enable the raising and lowering ofthe trencher.

11. Apparatus according to claim 8 wherein the trench retaining meanscomprises upright, spaced apart plates disposed on sides of the pipepassage, and including means permitting lateral movements of the aft endof the side plates about a vertical axis through the forward connectingmeans for the formation of curved trenches having relatively large radiiof curvature.

12. Apparatus according to claim 9 including a passage extensionextending forwardly of the throw-out means towards the pick-up means andterminating in an outwardly flaring mouth portion for guiding the pipefrom the pick-up means to the passageway.

1. Apparatus for laying relatively rigid, continuous lengths of pipebelow ground with a towing vehicle having a vehicle frame spaced aboveground between forward and aft traction means, the apparatus comprising:an elongate, rigid, narrow body having a forward end and an aft end,ground moving means forming an integral part of the body for forming atrench in the ground through which the body can be drawn, a tubularpassage for the pipe including a tubular member projecting forward ofthe forward end and terminating in a pipe receiving mouth portion forguiding the pipe into the tubular passage, the passage extending overthe length of the body, sloping rearwardly and downwardly from an upperforward end of the body and terminating in a substantially horizontalposition at the lower aft end of the body, the passage having acurvature of a sufficient curvature radius so that pipe in the passageis only elastically deflected, first mounting means for connection ofthe forward end of the body to the frame aft of the forward tractionmeans, and second mounting means spaced rearwardly of the first mountingmeans for connection of an intermediate body portion to the frame aft ofthe first mounting means and forward of the aft traction means tothereby firmly guide and position the apparatus and control theorientation and depth of the trench formed by the ground moving meanswhile enabling continuous lengths of relatively rigid pipe to passthrough the passage into the trench.
 2. Apparatus according to claim 1wherein the second mounting means includes means permitting lateralmovements of an aft portion of the body with respect to a vertical axisthrough the first mounting means to enable the formation of curvedtrenches.
 3. Apparatus according to claim 1 wherein the ground movingmeans comprises a substantially flat throw-out plate mounted to theforward end in a forwardly and downwardly sloping position for liftingand throw-out of ground to form the trench whereby lateral pressureagainst the body and friction are reduced.
 4. Apparatus according toclaim 1 wherein the passage has a rectangular cross-section and a heightexceeding its width.
 5. Apparatus according to claim 1 wherein the firstmounting means comprises a mounting bracket pivotable about asubstantially horizontal axis and secured to the body portion adjacentthe forward end, and including at least three upright connection membersarranged in a wedge formation through mating apertures in a yoke of thedrawing vehicle.
 6. Apparatus for connectIon to a draw vehicle having amain frame, forward and aft tracking means and a raiseable yoke disposedbelow the frame and intermediate the tracking means, the yoke includingmeans for attaching working accessories thereto, the apparatuscomprising: trench forming means for expelling a volume of ground toform an elongate trench when the vehicle moves over the ground, meanspositioning the trench forming means aft of the forward tracking meansand securing the trench forming means to the yoke, means defining anelongate passageway sloping rearwardly and downwardly, the passagewayextending over substantially the full length of the trench formingmeans, the passageway terminating in a substantially horizontal aft endsection rearwardly of the trench forming means and having a radius ofcurvature sufficiently large to effect elastic deformation of semi-rigidand rigid pipe passing through the passageway, means connecting thepassage defining means with the trench forming means, and means spacedrearwardly of the first connection means, attached to the yoke andconnected to an aft portion of the trench forming means forsubstantially rigidly holding an aft portion of the trench forming meansagainst vertical movement to guide and stabilize the trench formingmeans when it is drawn through the ground.
 7. Apparatus according toclaim 6 wherein the passage defining means includes means defining asubstantially rectangular passageway having a height exceeding its widthfor movement of pipes including T-fittings through the passageway andfor a desired orientation to the T-fittings.
 8. Apparatus for laying acontinuous rigid pipe string in a trench comprising in combination: adrawing vehicle having an elevated frame, forward and aft support wheelssupporting the frame above ground, and drive means for the wheels; anelongate, rigid trencher disposed beneath the frame and intermediate theforward and aft wheels, the trencher including a substantially flat,forwardly and downwardly sloping plate for the throw-out of soil fromthe trench and means maintaining a predetermined trench shape over adistance rearward of the throw-out plate; a gently curved, downwardlyand rearwardly sloping pipe passage extending over substantially thefull length of the trencher from an upper forward end to a substantiallyhorizontal aft lower end substantially flush with a trench bottom, thepassageway being enclosed by the trench form maintaining means, theradius of curvature of the pipe passage being sufficiently large so thatpipe in the passage is only elastically deformed and returns to itsoriginal shape upon discharge from the passage; means connecting aforward trencher end to the frame at a location on the frame forward ofthe aft wheels for stabilization of the trencher when it is drawnthrough the ground and maintaining the depth of the trench bottomsubstantially constant.
 9. Apparatus according to claim 8 wherein thepassage defining means is positioned so that relatively rigid pipeextending forward of the forward trencher end extends above a forwardwheel axis, and further including pick-up means movably supporting asection of substantially rigid pipe forward of the wheel axis at anelevation enabling elastic deflection of a continuous length of pipefrom the passage defining means over the pick-up means and onto theground supporting the pipe string.
 10. Apparatus according to claim 9including a vertically movable yoke carried by the frame and wherein thefirst and second connection means connect the trencher to the yoke toenable the raising and lowering of the trencher.
 11. Apparatus accordingto claim 8 wherein the trench retaining means comprises upright, spacedapart plates disposed on sides of the pipe passage, and including meanspermitting lateral movements of the aft end of the side plates about avertical axis through the forward connecting means for the formation ofcurved trenches having relatively large radii of curvature. 12.Apparatus according to claim 9 including a passage extension extendingforwardly of the throw-out means towards the pick-up means andterminating in an outwardly flaring mouth portion for guiding the pipefrom the pick-up means to the passageway.